EQUULEUS (EQUilibriUm Lunar-Earth point 6U Spacecraft) will be the world’s smallest spacecraft to explore the Earth―Moon Lagrange point. The spacecraft is being jointly developed by JAXA and the University of Tokyo and will be launched by NASA’s SLS (Space Launch System) EM-1 (Exploration Mission-1). The spacecraft will fly to a libration orbit around the Earth―Moon Lagrange point L2 (EML2) and demonstrate trajectory control techniques within the Sun-Earth-Moon region for the first time by a nano spacecraft. This spacecraft also carries several scientific observation missions which will be conducted during and after the flight to EML2; imaging of the entire Earth’s plasmasphere by extreme UV wavelength, observation of the space dust flux in the cis-lunar region, and observation of the lunar meteor impact flashes at the far side of the moon from EML2. The development of the spacecraft started in the summer of 2016 and the engineering model integration and testing was completed by the end of 2017. The design of the flight model was completed based on the engineering model test results. The integration and testing of the flight model will be completed by the end of 2018, to be ready for the launch by SLS’ first flight in 2019.